The present invention relates to a method of enhancing the dynamic range of intermodulation distortion measurements.
Intermodulation distortion (IMD), especially in the form of adjacent-channel power ratio (ACPR), is an important specification for cellular base stations, especially for the power amplifier. Suppliers must demonstrate that they meet these specifications.
The specifications for some of the newer communications formats, such as many forms of wideband CDMA and for multi-carrier base stations, dictate levels of ACP that seriously challenge the ability of test equipment to perform the measurement. Similar considerations apply to measuring other parameters that quantize intermodulation distortion effects, including multi-tone methods and noise power ratio.
The present invention provides a technique for measuring ACP and other forms of IMD of amplifiers and other two-port devices. The technique, which uses standard equipment, enhances the traditional dynamic range of measurement by at least 25 dB.